1. Field of the Invention
The present invention relates to a battery pack which includes cylindrical battery cells arranged in two rows and four layers, the battery cells in each of battery cell pairs being connected in parallel, and the four pairs of the parallel-connected battery cells being connected in series.
2. Description of the Related Art
A battery pack includes a plurality of cylindrical battery cells, electrode tabs for electrically connecting terminals of the battery cells arranged in a certain manner, a lower case for containing the battery cells electrically connected through the electrode tabs, and an upper cover for covering the lower case in which the battery cells are contained, and is detachably attached to a mount part provided at the back side of an electronic apparatus such as a video camera for business use, to be used as a power source for the electronic apparatus (refer to Japanese Patent Laid-Open No. 2003-257388, hereinafter referred to as Patent Document 1).
The battery pack for use in an electronic apparatus such as a video camera for business use needs to have a rated voltage of about 14.4 V. Therefore, since a battery cell composed of a cylindrical lithium ion secondary cell, for example, has a rated voltage of about 3.6 V, four such battery cells should be connected in series in order to realize the rated voltage of about 14.4 V. In view of this, in the battery pack disclosed in Patent Document 1, battery cells are arranged in four rows and two layers, the battery cells in each of battery cell pairs are connected in parallel through a main circuit board, and the four pairs of parallel-connected battery cells are sequentially connected in series.
In the battery pack described in Patent Document 1, however, the arrangement of the battery cells in four rows and two layers results in an increased insertion area at an insertion end relevant to insertion of the battery pack into a mount part in a video camera, so that the mount part of the video camera should have an enlarged area. In the battery pack described in Patent Document 1, therefore, restrictions may be exerted on arrangement of operating buttons and the like at a mount surface of the video camera to which the battery pack is to be mounted.